One more safety issue I've been wondering about and perhaps the clever guys have a solution.

What if Mr. do-it-yourself unintentionally connects his generator to the grid and feeds power back in the event of a Neutral break down the road (before the utility transformer). How will I be able to protect myself and my equipment if there starts to flow 115V from his installation into my house?

Would it be as simple as to 'always assume circuits are live' or is there some other method to prevent being lit up like a light bulb if you touch Neutral by accident?

This is a interesting question - falls right into the other chats we have re. registering and why and NRS regulations and all that.

I am pretty sure there are a Mr. do-it-yourself or two out there who has done this unintentionally already - and no-one knows it.

 

Pal of mine lost fridge / freezer and a few computers during Eskom failures a long while back. Accidentally they discovered one day that when Eskom was supposedly off, that they still had some volts on the plugs, 115v if memory serves, causing the drama.

It allegedly came from a newly installed wind farm close by the town that kept on feeding back into the grid when Eskom was off and the wind blew.

There are voltage relays that you can get from electrical places and they are not especially expensive. You could use that to protect yourself from a low voltage condition.

7 hours ago, plonkster said:

There are voltage relays that you can get from electrical places and they are not especially expensive. You could use that to protect yourself from a low voltage condition.

Can you please explain a bit more on this?

Would a Ziehl device also do the same function as I can see this to be a possible requirement in the future if you don't have a certified inverter (referring to another discussion on CoCT requirements on the forum).

3 hours ago, Ingo said:

Can you please explain a bit more on this?

You could probably pick one up at a local AC/DC express (or whatever), I've seen some for as little as R500. Here is an example of what I am thinking of.

3 hours ago, Ingo said:

Would a Ziehl device also do the same function as I can see this to be a possible requirement in the future if you don't have a certified inverter (referring to another discussion on CoCT requirements on the forum).

Yes, the Ziehl does all this and more. It checks not only voltage, but also frequency, and it also checks RoCoF (rate of change of frequency, that is the second derivative). The Ziehl is overkill, but it will do the job.

Edit: WIth regards to using a Ziehl with a non-certified inverter, you can only do this if the inverter itself implements at least one active anti-islanding measure. The reason the Ziehl is on the CoCT list is because the local Victron guy put it there, because it is used with the Multiplus and the Quattro (they implement active measures). Owners of other inverters might have to check before spending money.

Edited January 6, 20197 yr by plonkster

Would that unit you have in mind be sufficient as one leg of the two-stage anti-island requirement? That Ziehl device is very costly. If I can do with this unit, a MCB and a contactor I would probably be R5k happier.

Surely Mr. DIY's generator will just trip, trying to supply the whole suburb with power?

It's a strange sort of set up.

Passive methods including at least 1 active method.

In this context passive means monitoring say, the voltage and frequency to be within certain boundaries.

Simple and well (relatively?) cheap.

The problem is there is a small chance that your system is such harmonious balance that you remain within these boundaries, within the (NDZ) or Non-Detection Zone window.

So active methods step up to the plate, in one of two basic forms:

1. Some sort of continuous power line signal communication from the grid-side that is monitored on the IPP side.

(This is an impractical option due to costs and obtaining the utility's permission for equipment installed on their side).

2. The inverter itself tries to impose changes on incoming grid power and based on whether or not it can actually do so, it decides if the inertia of the grid is present.

( There are a number of methodology's,  but whichever is employed, this is the practical solution within the IPP's control).

And this creates a sort of circular problem, option 1 could be performed by another device, but (the way I see it), option 2 requires an inverter.

This active method requires a power source, and makes use of filters that are already present in an inverter.

It basically says that in order to qualify for an inverter, you need an inverter. (granted one that is capable).

It appears that there is no other component available that will pre-qualify one for a inverter. 

So you pay your considerable amount of money for your system, and that's what's at risk of not being compliant.

I'd like to see a pre-qualifying device, that doesn't require one to take such a financial plunge on the actual inverter itself.

Something that does not require an external power source to perform this injection.

I think there is a lot of room in the market for a  reasonably priced gateway device that resolves this "active" requirement.

Anyone know of anything?

 

 

1 hour ago, Ingo said:

Would that unit you have in mind be sufficient as one leg of the two-stage anti-island requirement?

Well... no... there is a little seemingly innocuous statement in the requirements:

Quote

4.2.2.2.4 A single failure within the disconnection switching unit shall not lead to failure to disconnect. Failures with one common cause shall be taken into account and addressed through adequate redundancy.

And these cheaper monitoring relays usually has no such redundancy built in.

1 hour ago, dax021 said:

Surely Mr. DIY's generator will just trip, trying to supply the whole suburb with power?

Right. Unless it trips in precisely such a way that you have a small enough island, say two or three houses. The regulations always seems to cater for that kind of thing too.

Does that mean a Quattro HAS to have a Ziehl to be fully compliant?

5 minutes ago, Ingo said:

Does that mean a Quattro HAS to have a Ziehl to be fully compliant?

Jip, if you are in CoCT.

6 minutes ago, Ingo said:

Does that mean a Quattro HAS to have a Ziehl to be fully compliant?

Yup. Because of this:

Quote

4.2.2.2.5 The disconnection switching unit shall disconnect from the network by means of two series switches. Each switch shall be separately rated to the embedded generator’s nominal poweroutput. At least one of the switches shall be an electromechanical switch while the second switch may be part of the existing solid state switching circuits of a utility-interconnected static power converter. The electromechanical switch shall disconnect the embedded generator on the neutral and the live wire(s).

The Multiplus (not the Multigrid or the Multiplus-II) and the Quattro has only one switching unit. In most countries that is sufficient, but not in all (Germany and South Africa being two of those where it isn't good enough).

Noted, thanks.